The present invention relates in general to object-oriented programming and architectures and more particularly to a method of moving objects in a computer network.
In object-oriented programming, real world objects are modeled by software objects that have encapsulated therein special procedures and data elements. In object-oriented programming jargon, procedures are referred to as methods. To avoid having to redefine the same methods and data members for each and every occurrence of an object, object-oriented programming provides the concept of classes. An inheritance structure of one or more levels of increasingly more specialized classes is created to provide templates that define the methods and variables to be included in the objects of each class. Therefore, an object belonging to a class is a member of that class, and contains the special behavior defined by the class. In this manner, each object is an instance of a defined class or template and the need to redefine the methods and data members for each occurrence of the object is eliminated.
With the rise of distributed systems, client/server computing, and internet/intranet interactions, inter-node communications between applications have become a prerequisite. Early operating systems lacked support for inter-application communications, forcing software developers to write custom code to perform remote procedure call (RPC) for each and every application that needed remote communications.
Microsoft(trademark) has developed DCOM(trademark) (Distributed COM) to support inter-application communications across networked computer systems. Another technology standard for inter-object communications is CORBA(trademark) (Common Object Request Broker Architecture) established by the Object Management Group (OMG) sponsored by more than 660 companies, including Digital Equipment Corporation(trademark), Hewlett Packard(trademark), IBM(trademark), and. Sun Microsystems, Inc(trademark). CORBA defines how messages from one object to another are to be formatted and how to guarantee delivery. The messaging in CORBA is performed by object request brokers (ORBs). ORBs receive messages to determine the location of the receiving object, route the message, and perform all necessary platform and language translations. In object technology, a message is typically a request sent to an object to change its state or return a value. The object has encapsulated methods to implement the response to the received messages. Through technologies such as DCOM(trademark) and CORBAT(trademark), objects can communicate with remote objects residing in other computer platforms connected by a network. However, a serious drawback of these objects under the conventional ORB technology is that they do not support the concept of mobility and therefore cannot move around the network to other computer platforms.
Enter the concept of agents. Agents are defined as specialized objects that possess the characteristic of autonomy. Autonomy is the ability to program an agent with one or more goals that it will attempt to satisfy, even when it has moved into a network onto other platforms and has lost all contact with its creator. General Magic, Inc.(trademark) of Sunnyvale, Calif. has developed a set of interpreted object-oriented computer instructions called Telescript(trademark). By using Telescript(trademark) computer instructions, an agent may move from one place to another place by specifying the destination address, name, and/or class. However in Telescript(trademark), agents cannot communicate remotely across the network. In other words, Telescript agents must occupy the same place in order for them to interact. Further, in order for two agents to interact, they must travel to a pre-established place known to both agents. This presents some very serious restrictions to the ability for agents to communicate with one another.
Another agent technology called Aglets(trademark) has been introduced by IBM(trademark). A significant difference between Aglets(trademark) and Telescript(trademark) is that Aglets is based on Java(trademark), Sun Microsystems Inc.""s computer programming language. Although Aglets(trademark) allows agent movement across the network, the destination must be a pre-established place known to the agent as in Telescript(trademark). Further, Aglets(trademark) agents also may not communicate remotely across the network with regular Java method invocation syntax. Again, these serious restrictions make Aglets(trademark) very inflexible in inter-agent communications.
From the foregoing, it may be appreciated that a need has arisen for an autonomous and mobile agent architecture in an object-oriented programming environment. In accordance with the present invention, a method of moving objects in a computer network is provided that substantially eliminates or reduces disadvantages and problems associated with conventional mobile agent technology.
According to an embodiment of the present invention, there is provided a method of moving objects in a computer network that includes receiving a move indication at an object to move to a new host address and port number within the computer network from a current host address and port number within the computer network. Upon receiving the move indication, the object determines its availability to move. If available to move, a serialized version of the object is created and an old version of the object is retained at the current host address and port number. The serialized version of the object is sent to the new host address and port number and a new version of the object is created at the new host address and port number from the serialized version of the object. Upon establishment of the new version of the object at the new host address and port number, the old version of the object is de-registered from the current host address and port number. If forwarding is desired, the old version of the object creates a secretary object that takes care of forwarding messages to the new version of the object at the new host address and port number that were sent to the old version of the object at the current host address and port number.
The present invention provides various technical advantages over conventional mobile agent technology. For example, one technical advantage is to provide movement of objects in a computer network. Another technical advantage is to create a secretary object to handle message forwarding to the moved object. Yet another technical advantage is to retain an old version of the object at its current host address and port number during establishment of a new version of the object at the new host address and port number. Other technical advantages are readily apparent to those skilled in the art from the following figures, description, and claims.